Centrifugal gas compressors



3,251,539 CENTRIFUGAL GAS COMPRESSORS Robert W. Wolfe, Pittsburgh, Pa., and Robert R. Young,

Staunton, Va., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed May 15, 1963, Ser. No. 280,606 5 Claims. (Cl. 230-114) This invention relates to centrifugal gas compressors, and relates more particularly to centrifugal refrigerant compressors.

Centrifugal gas compressors have radially extending passages around the tips of the blades on their rotors, known as radial diffuser. Such diffusers are designed for maximum flow rates. The loads on centrifugal refrigerant compressors vary over a wide range, and they may be operated at such low flow rates that their diffusers are too large for efiicient operation, and stall pulsations may occur in their rotors, causing vibrations and noise. I Adjustable spin inducing vanes are widely used for reducing the output volumes of constant speed, centrifugal gas compressors. The advantages and method of operation of such vanes are fully disclosed in the Hagen Patents Nos. 1,846,863 and 1,989,413.

A centrifugal refrigerant compressor embodying this invention uses such spin inducing vanes for reducing-its output volume or flow rate, and noise and vibrations at low flow rates are prevented by connecting the spin vane adjusting mechanism to a movable outer wall of the radial diffuser of the compressor so that as the spin vanes are moved to approach closed positions for reducing flow rates near minimum, the outer wall of the diffuser is moved closer to its inner wall to decrease the width of the diffuser for increasing the velocity of the gas flowing through the diffuser.

An object of this invention is to increase the overall efficiency of a centrifugal gas compressor.

Another object of this invention is to increase the efficiency of a centrifugal gas compressor at low flow rates.

Another object of this invention is to prevent the occurrence of stall pulsations at low flow rates in centrifugal gas compressors.

This invention will now be described with reference to the annexed drawings, of which:

FIG. 1 is a fragmentary side view, in section, of a centrifugal refrigerant compressor embodying this invention, with its spin vanes shown in wide open position, and its radial diffuser shown in its widest position, and

FIG; 2 is an enlarged view of the upper portion of FIG. 1, with its spin vanes shown in closed positions, and its radial diffuser shown in its narrowest position.

The compressor has an outer end wall forming a converging, axial inlet passage 11. Spin inducing vanes 12 are supported for rotation within the inner end portion of the passage 11, on the inner ends of radially extending pivot rods 14 which are journalled for rotation within the wall 10. The rods 14 have arms 15 on their outer ends. The arms 15 have pivot pins 16 extending outwardly therefrom, off-set from the rods 14.

The compressor has a rotor 18 with radially extending blades 19 supported between a curved hub 20 and a correspondingly curved front plate 21. The hub 20 is attached to a shaft 22 which is connected through a step-up gear box which is not shown, to an electric motor which is not shown. The outer end of the front plate is formed as an annular ring 24 which is in contact with an annular seal 25 which extends around the ring 24 concentric therewith, the seal being supported at the inner end of the wall 10.

United States Patent 0 ice The blades 19 discharge into radial diffuser 26 which extends around the tips of the blades. The diffuser discharges into a scroll-shaped outlet passage 29. Casing wall 28 forms the inner Wall of the passage 29. The inner surface of a ring 30 forms the outer surface of the diffuser 26, and has a cylindrical outer end portion 31 slidable along cylindrical inner portion 32 of a wall 34 which extends ,aroundthe inner end portion of the wall 10 and around the outer portion 31 of the ring 30. The wall 34 is attached by bolts 35 to a casing wall 36 which extends around the wall 28 and around a wall 37 forming the outer wall of the passage 29. The wall 34 is attached by bolts 38, one of which is shown by FIG. 1, to the wall 10. The Wall 34 has an inwardly protruding portion 39 with a cylindrical surface 38 around and in slidable contact with inner cylindrical surface 40 of a ring-shaped piston 41 which has an outer cylindrical surface 42 around and slidable along cylindrical surf-ace 43 of the wall 10. The piston 41 has an outer end portion 44 with an outer cylindrical surface 45 which extends around and in slidable cont-act with inner cylindrical surface 46 of the wall 34. A fluid passage 48 is formed around the piston 41 between the wall portion 39 and the piston portion 44, and connects with a fluid inlet passage 49 in the wall 34. Another fluid passage 50 is formed between the outer end of the piston 41 and an outer portion 51 of the wall 10, and which connects with a fluid inlet passage 52 in the wall 34.

The pins 16 of the spin vane rotating arms 15 are rotata'bly positioned within an annulus 54 in the piston 41.

A ring 56 has a cylindrical inner end portion 57 in contact with a cylindrical surface 58 of the ring 30, and its inner end contacts a retainer ring 59 partially recessed in the ring 30. The ring 30 has an annulus 65 into which extend inner ends of pins 66 which extend radially within the wall 34. The .pins 66 when contacting the inner edge of the annulus 65 as shown by FIG. 1, limit the extent of the outward movement of the diffuser ring 30, and

.which is attached a streamlining fairing 62 which extends around the outer end portion of the shaft, and has a rounded nose which extends into the passage 11.

When the compressor is operating under full load, the.

spin vanes 12 are in their fully opened position, and the diffuser 26 is in its widest position as shown by FIG. 1. When the output of the compressor is to be reduced, oil under pressure from a conventional source which is not shown, is supplied through the passage 52 into the passage 50 against the outer end of the piston 41, causing the latter to move inwardly, and to rotate through the pins 16, the arms 15 and the pivot rods 14, the spin vanes 12 towards closed position, producing spin in the gas entering the rotor 18, and thereby reducing the volume of gas moved by the rotor.

When the piston has moved inwardly a sufficient distance to have adjusted the vanes 12 to near closed position, its inner end moves against the outer end of the ring 56 and moves the latter and the diffuser ring 30 inwardly towards the wall 28, decreasing the width of the diffuser 26, and increasing the velocity of the reduced gas volume passing through it. This prevents the previously experienced stall pulsations which occur at low output volumes. When the piston 41 has moved inwardly sufliciently to have adjusted the spin vanes to their closed position, it moves the rings 56 and 30 further todiffuser 26 as shown by FIG. 2.

When the output of the compressor is to be again increased, oil under pressure is supplied .through the passage 49 into the passage 48 against the inner end of the piston portion 44, causing the piston 41 to move outwardly and to adjust the spin vanes towards open position, the supply of oil through the passage 52 being discontinued. The pressure of the gas within the diffuser moves the diffuser ring 30 outwardly at this time so that as the gas volume increases in the lower output range, the width of the diffuser is increased.

Narrowing the width of the diffuser at low output volumes not only prevents undesired vibrations and noise, but increases the efiiciency of the compressor at such low output volumes.

Wh-at is claimed is:

1. A centrifugal gas compressor comprising a rotor having radial flow blades, means forming an axial gas inlet passage to said rotor, means including movable outer and fixed inner casing walls forming a radial diffuser around the tips of said blades, spin vanes supported for rotation in said passage, means movable towards said outer wall for rotating said vanes from open towards closed position, and means in contact with said outer wall and normally spaced from said movable means and contacted by said movable means when the latter has rotated said vanes a predetermined distance towards closed position for moving said outer wall towards said inner wall.

2. A centrifugal gas compressor comprising a rotor having radial flow blades, means forming an axial gas inlet passage to said rotor, means including movable outer and fixed inner casing walls forming a radial diffuser around the tips of said blades, spin vanes supported for rotation in said passage, means forming a cylindrical surface around the inner end portion of said passage and said v-anes concentric with said rotor, means in slidable contact with said surface for rotating said vanes from open towards closed position, and means including said last mentioned means for moving said outer wall towards said inner wall when said vanes have been rotated a predetermined distance towards closed position.

3. A centrifugal gas compressor as claimed in claim 2 in which said means in slidable contact is an annular piston, in which means is provided for supplying fluid under pressure against a portion of said piston for moving said piston towards said outer wall for rotating said vanes from said open towards said closed position, and in which means is provided for supplying fluid under pressure against another portion of said piston for moving said piston in the opposite direction for rotating said vanes from closed towards open position.

4. A centrifugal gas compressor comprising a rotor having radial flow blades, a casing wall forming an axial gas inlet passage to said rotor, means including movable outer and fixed inner casing walls forming a radial diffuser around the tips of said blades, said first mentioned wall having a cylindrical surface around an outer end portion of said passage, an annular piston having a cylindrical inner surface around and in slidable contact with said first mentioned surface, spin vanes having radially extendingpivot rods journalled for rotation in said first mentioned wall, said vanes extending into said passage near its inner end, said first mentioned wall having an annular recess forming a clearance space around which the inner end portion of said piston extends, vane rotating arms in said space attached to the outer ends of said rods, pins attached to said arms and extending radially therefrom off-set from said rods, said piston having an annulus into which the outer ends of said pins extend, means for supplying fluid under pressure against a portion of said piston for moving said piston towards said movable wall for rotating said vanes from open towards closed position, means normally spaced from the inner end of said piston and contacted by said inner end of said piston when said piston has moved towards said movable wall a sufficient distance to have rotated said vanes a predetermined distance towards closed position for moving said movable wall towards said fixed wall on further movement of said piston towards said movable wall, and means for supplying fluid under pressure against another portion of said piston for moving said piston in a direction away from said movable wall.

5. A gas compressor as claimed in claim 4 in which said piston has an outer cylindrical surface, in which there is another c-asing wall having an inner cylindrical surface around and inslidable contact with said last mentioned surface, and in which said means for supplying fluid under pressure includes spaced-apart openings in said last mentioned walls.

References Cited by the Examiner UNITED STATES PATENTS 2,438,442 3/ 1948 Holt 103-97 2,455,251 11/1948 Hersey 230-114 2,645,410 7/1953 Bauger et a1 230-114 2,770,943 11/1956 Beale 253-52 2,815,188 12/1957 Nelson 253-59 2,947,466 8/ 1960 Busquet 230-114 3,032,259 5/1962 Jassniker 253-52 3,071,345 1/1963 Glenn et al 230-114 SAMUEL LEVINE, Primary Examiner. DONLEY J. STOCKING, Examiner. W. L. FREEH, Assistant Examiner. 

1. A CENTRIFUGAL GAS COMPRESSOR COMPRISING A ROTOR HAVING RADIAL FLOW BLADES, MEANS FORMING AN AXIAL GAS INLET PASSAGE TO SAID ROTOR, MEANS INCLUDING MOVABLE OUTER AND FIXED INNER CASING WALLS FORMING A RADIAL DIFFUSER AROUND THE TIPS OF SAID BLADES, SPIN VANES SUPPORTED FOR ROTATION IN SAID PASSAGE, MEANS MOVABLE TOWARDS SAID OUTER WALL FOR ROTATING SAID VANES FROM OPEN TOWARDS CLOSED POSITION, AND MEANS IN CONTACT WITH SAID OUTER WALL AND NORMALLY SPACED FROM SAID MOVABLE MEANS AND COMTACTED BY SAID MOVABLE MEANS WHEN THE LATTER HAS ROTATED SAID VANES A PREDETERMIONED DISTANCE TOWARDS CLOSED POSITION FOR MOVING SAID OUTER WALL TOWARDS SAID INNER WALL. 